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Abstract:

We deployed three eddy covariance towers along a burn severity gradient (i.e. severely-, moderately-, and un-burned tundra) to monitor post fire Net Ecosystem Exchange of CO2 (NEE) within the large 2007 Anaktuvuk River fire scar during the summer of 2008. This data represents the 2011 post fire energy and mass exchange at the moderate burn site.

Keywords:

Arctic LTER keywords:

Date Range:

Friday, January 1, 2010 to Saturday, December 31, 2011

Publication Date:

2013

Methods:

We deployed three eddy covariance towers with identical instrumentation across a burn severity gradient (Rocha and Shaver 2009). The three sites (i.e. Severe burn, Moderate burn, and Unburned) were 40 km to the west of the nearest road and were selected during a helicopter survey of the southern area of the Anaktuvuk River Fire scar in late May 2008 (Figure 1; Table 1). Because the fire had burned through September of the previous year, initial deployment of flux towers occurred prior to any significant vegetative regrowth, and our sampling campaign captured the full 2008 growing season (June 1-August 28). Each site was equipped with a Campbell Scientific® CR5000 datalogger that recorded data from micrometeorological instrumentation located on a stainless steel tripod (CM110; Campbell Scientific; Logan Utah, USA) at a height of 2.6 m. Data were stored on a 2 Gb PCMCIA card and downloaded every two to three weeks. Power for the datalogger and instrumentation was located 15 m to the east or west of the tower and consisted of a south-facing solar panel and two 12 V 80 amp-hour batteries enclosed in a polyethylene box. Towers ran continuously through the summer of 2008 with the exception of the severe burn site, which was damaged by a bear during the last week of August. The towers have been in operation since June 2008.

Environmental data were recorded as half hour averages. Net radiation was monitored with a NRLITE net radiometer (Campbell Scientific; Logan Utah, USA). Incoming and reflected solar and longwave radiation were measured with a CNR-1 Radiometer (Campbell Scientific; Logan Utah, USA), while incoming and reflected Photosynthetically Active Radiation (PAR) were measured with a silicon quantum sensor (LI-COR; Lincoln, NE, USA). Air temperature and relative humidity was measured with an HMP45C-L sensor (Campbell Scientific; Logan Utah, USA) enclosed in a naturally aspirated radiation shield, while precipitation was measured with a tipping bucket rain gauge (TE525; Campbell Scientific; Logan Utah, USA). Volumetric water content at a depth of 2.5 cm was measured with two reflectometers (CS616; Campbell Scientfic; Logan Utah, USA), soil temperature at a depth of 2 and 6 cm was measured with two averaging soil thermocouples (TCAV-L; Campbell Scientific; Logan, Utah, USA), and soil heat flux at a depth of 8 cm was measured with four soil heat flux plates (HFP01; Campbell Scientific; Logan, Utah, USA). Measurements of the soil environment were recorded on separate CR1000 dataloggers at the severely and moderately burned sites.

Turbulent fluxes of momentum, sensible heat, latent heat and CO2 were determined by the eddy covariance technique (Baldocchi et al. 1988). Half hourly CO2 and H2O fluxes were calculated as the covariance between the turbulent departures from the mean of the 10 Hz vertical wind speed measured with a 3D sonic anemometer (CSAT3; Campbell Scientific; Logan, Utah, USA) and the CO2 and H2O mixing ratio measured with an open path InfraRed Gas Analyzer (IRGA; LI7500; LI-COR; Lincoln, NE, USA). Fluxes were processed using EdiRe software (University of Edinburgh; Moncrieff et al. 1997) and reported using the meteorological sign convention where negative NEE indicates carbon uptake and positive NEE indicates carbon loss from the ecosystem. Ten Hz data were despiked, rotated to the mean wind streamlines, and corrected for the density effect due to sensible heat transfer (i.e. WPL correction; Webb et al. 1980). Turbulent fluxes of sensible and latent heat captured 78 to 80% of the available energy at each of the sites, which is consistent with energy budget closure observed for other eddy covariance studies (Wilson et al. 2002).

The moderate burn site is comprised of a mosaic of partially and completely burnt moss patches scattered across the landscape that varied in size from ~1 to 10 m2. Partially burnt moss cover was 33% and was dominated by Sphagnum [Sphagnum spp.] and feather mosses [Hylocomium spp.]. Recovering and dead tussocks formed the dominant canopy cover. Intertussock area was composed of burnt duff (30% of ground cover) and several herbaceous species (Cloudberry; Labrador tea, and Cranberry [Vaccinium vitis-idaea L.]). All tussocks were scorched in the fire and 95% of tussocks recovered after the first growing season.

Variable Details

(Variables names are in the first line/row of the CSV file and Excel data sheet.)

Year

Label: Year

Definition: Year

Type: Physical quantity

Unit: number

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values: None specified

DOY

Label: DOY

Definition: Unitless Fractional Day of Year from January 1, 2008

Type: Physical quantity

Unit: number

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values: None specified

Pressure

Label: Pressure

Definition: Atmospheric pressure

Type: Physical quantity

Unit: kilopascal

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = MISSING OR NOT MEASURED

Air Temperature

Label: Air Temperature

Definition: Air temperature at 2.6m

Type: Physical quantity

Unit: celsius

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = MISSING OR NOT MEASURED

Surface Temperature (Apogee)

Label: Surface Temperature (Apogee)

Definition: Kelvin degrees at surface

Type: Physical quantity

Unit: kelvin

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = MISSING OR NOT MEASURED

Soil Temperature

Label: Soil Temperature

Definition: Soil Temperature-Average of 2cm and 6cm measurements

Type: Physical quantity

Unit: celsius

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = MISSING OR NOT MEASURED

Ambient Vapor Pressure

Label: Ambient Vapor Pressure

Definition: Ambient Vapor Pressure

Type: Physical quantity

Unit: kilopascal

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = MISSING OR NOT MEASURED

Incoming Shortwave

Label: Incoming Shortwave

Definition: Incoming Shortwave

Type: Physical quantity

Unit: wattPerMeterSquared

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = MISSING OR NOT MEASURED

Outgoing Shortwave

Label: Outgoing Shortwave

Definition: Outgoing Shortwave

Type: Physical quantity

Unit: wattPerMeterSquared

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = MISSING OR NOT MEASURED

Incoming Longwave

Label: Incoming Longwave

Definition: Incoming Longwave

Type: Physical quantity

Unit: micromolePerMeterSquaredPerSecond

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = MISSING OR NOT MEASURED

Outgoing Longwave

Label: Outgoing Longwave

Definition: Outgoing Longwave

Type: Physical quantity

Unit: micromolePerMeterSquaredPerSecond

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = MISSING OR NOT MEASURED

Net Radiation

Label: Net Radiation

Definition: Net Radiation

Type: Physical quantity

Unit: wattPerMeterSquared

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = MISSING OR NOT MEASURED

Incoming PAR

Label: Incoming PAR

Definition: Incoming photosynthetically active radiation

Type: Physical quantity

Unit: micromolePerMeterSquaredPerSecond

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = MISSING OR NOT MEASURED

Outgoing PAR

Label: Outgoing PAR

Definition: Outgoing photosynthetically active radiation

Type: Physical quantity

Unit: micromolePerMeterSquaredPerSecond

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = MISSING OR NOT MEASURED

IRGA AGC

Label: IRGA AGC

Definition: Count of IRGA AGC flag

Type: Physical quantity

Unit: number

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = MISSING OR NOT MEASURED

Friction Velocity

Label: Friction Velocity

Definition: Calculated friction velocity

Type: Physical quantity

Unit: meterSquaredPerSecond

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = MISSING OR NOT MEASURED

Wind Direction

Label: Wind Direction

Definition: Sonic pointed North

Type: Physical quantity

Unit: degree

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = MISSING OR NOT MEASURED

Wind Speed

Label: Wind Speed

Definition: Wind Speed

Type: Physical quantity

Unit: meterPerSecond

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = MISSING OR NOT MEASURED

Latent Heat Flux

Label: Latent Heat Flux

Definition: Latent Heat Flux

Type: Physical quantity

Unit: wattPerMeterSquared

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = MISSING OR NOT MEASURED

Sensible Heat Flux

Label: Sensible Heat Flux

Definition: Sensible Heat Flux

Type: Physical quantity

Unit: wattPerMeterSquared

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = MISSING OR NOT MEASURED

Ground Heat Flux

Label: Ground Heat Flux

Definition: Ground Heat Flux

Type: Physical quantity

Unit: wattPerMeterSquared

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = MISSING OR NOT MEASURED

Net Ecosystem Exchange of CO2

Label: Net Ecosystem Exchange of CO2

Definition: Net Ecosystem Exchange of CO2

Type: Physical quantity

Unit: micromolePerMeterSquaredPerSecond

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = MISSING OR NOT MEASURED

This material is based upon work supported by the National Science Foundation under Grants #DEB-1637459, 1026843, 9810222, 9211775, 8702328; #OPP-9911278, 9911681, 9732281, 9615411, 9615563, 9615942, 9615949, 9400722, 9415411, 9318529; #BSR 9019055, 8806635, 8507493. Any opinions, findings, conclusions, or recommendations expressed in the material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.